I did a session yesterday on Entity Framework 4 using Visual Studio 2010 RC. Unfortunately VS2010 crashed on me 4 or 5 times during my presentation whilst editing code (I resolved it by copy and paste from Notepad!).
I was pretty convinced the issue was related in some weird way to the amount of other beta stuff I have on my machine plus a history of various CTP installs of VS2010. However it turns out there is a more fundamental problem with Intellisense in the release candidate.
The good news is we have made available a VS 2010 RC patch which fixes this issue. Or at least it did for me!
As a reminder, if you have issues with the VS 2010 RC please submit them via the connect.microsoft.com web-site.